There is a variety of environmental contaminants that are candidates for removal by the invention methods and compositions. Among these are odoriferous compounds with undesirable odors (malodors), organism contaminants such as molds and mildew, algae, spores, and the like.
Malodorous chemical compounds, all of which are in need of proper odor control technology, are classified in several ways which can include description of the malodor, common malodor name, chemical name, and/or the chemical formula. Malodorous compounds are classified as being primary odor causing agents comprising basal chemical structures (or functional groups), or secondary odor causing agents as the result of decay.
An example of primary odor causing agents of concern include: urine based malodors, comprised of ammonia (—NH3), or urea (NH2CONH2); putrid odors comprised of volatile fatty acids (R—COOH or derivatives including acetic acid, propanoic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, 2-ethyl butyrate, or ethanol); rotten egg odors comprising mercaptans (X—SH); total reduced sulfur compounds such as hydrogen sulphide (H2S), methyl mercaptan (CH3S—H), dimethyl sulphide (CH3—S—CH3) and dimethyl disulphide (CH3—S—S—CH3); fermenting perspiration odors comprised of diacetyl (2,3-butanedione, C4H6O2); fecal odors comprised of skatole (3-methyl-1H-indole, C9H9N); skunk odor comprised of tert-butyl mercaptan (2-methyl-2-propanethiol, C4H10S); rancid cheese, sweat, putrid odors comprised of isovaleric acid (3-methylbutanoic acid, C5H10O2); onion odor comprised of methional (3-methylthio), propionaldehyde, (C4H8OS); rotten fish odor comprised of trimethylamine (N,N-dimethylmethanamine, C3H9N); garlic odor comprised of allicin (2-propene-1-sulfinothioic acid S-2 propenylyester, C6H10OS2); and sour putrid odor comprised of pyridine (C5H5N), to name a few.
Secondary odor causing agents include: putrid odors comprised of putrescine (diaminobutane, C4H12N2); cadaver odor comprised of cadaverine (1,5-diaminopantene, C5H14N2); among others too numerous to mention but incorporated here by reference.
There is almost an unlimited number of primary and secondary odor causing agents many more than those listed above. This is especially true for secondary odor causing compounds owing their diversity to the flux of decay upon decomposition. There is the continued transition of odoriferous compounds as a result of decay. The number, type, and complexity of odoriferous compounds are further complicated by the potential dynamic transition of malodor from solid to liquid to gaseous form over time. The dynamic transition may be attributable to changes in the state of matter due to physical factors such as temperature or pressure, due to biological factors such as enzymatic or microbial breakdown, or due to entropic decay.
Most malodorous compounds, however, have the ability to hydrogen bond as part of their molecular structure with few exceptions. Hence, malodors, as such, have a nearly universal ability to form this type of association and this affords the means to bond malodors through this functionality no matter their shape, size, chemical composition or molecular weight. This ability is retained independent of the molecular diversity attributable to the flux of decay over time. Malodorous compounds, as such, may occur in either solid, liquid or gaseous forms and compounds may readily transition from one state of matter to another as part of the spontaneous decomposition of matter during molecular decay. This makes molecular recognition difficult from a mimetic standpoint in that the end-product of decay is a moving molecular target.
The simplest and most common approach for dealing with a malodor is to mask it by introducing a new odor stronger than the malodor. The result is an increase in the overall odor level but frequently both odors are discernible. The effect is short lived and the malodors still can be readily detected.
Another general approach for malodor control is to use chemical oxidation using materials such as sodium hypochlorite, chlorine dioxide, chloramine-T, hydrogen peroxide, sodium percarbonate or potassium permanganate are used to oxidize odoriferous compounds. The presumption with this approach is that the compounds involved in malodor are oxidizable. For example, U.S. Pat. Nos. 6,667,030; 6,743,420; and 6,296,841 disclose the use of compounds based on N-sodium, N-chloro-para-toluene-sulfonamide and N-sodium, N-chloro-para-benzenesulfonamide (e.g., chloramine-T) to neutralize certain malodorous materials. This is limited to mercaptans, sulfides, and amine-based compounds. In another example, Clorox Corporation employs odor locking mineral crystals (e.g., borates), along with fragrances, as an additive to bentonite clay in a formulation for cat litter (U.S. Pat. Nos. 4,949,672; 5,094,190; 5,176,108).
Oxidizing agents used to oxidize malodorous compounds tend to be very harsh; dangerous to use and are often incompatible with fabrics due to bleaching effects. Oxidation of malodors generally requires that the oxidizing agents be used at high concentration, but high concentrations of oxidizing agents such as chloramine-T can be harmful to fish, animals, people and the environment in general. Furthermore, use of oxidizing agents to control malodors provides a temporary solution at best, if it is even an effective solution at all.
A common variant of chemical oxidation for gaseous malodor compound control involves ozonation. Ozone emitting devices are commonly available for household and industrial use and involve the oxidation of chemical species with ozone free radicals, but high levels of ozone are known to be toxic to humans and animals upon prolonged exposure and cause cellular degeneration of mammalian tissue over time.
Absorption with bulk absorbents is another passive process that involves the uptake of liquids which may contain soluble odoriferous compounds. The bulk absorbent composite materials may be any material or structure that readily imbibes water. These can include fibers, clays, moisture absorbing polymers, or any liquid absorbing material or combinations. Absorption affords no specificity or selectivity or affinity for odoriferous compounds and their absorption is merely the result of being in solution as the solvent is absorbed. Odoriferous materials can desorb or leech out of the bulk absorbent over time due to evaporation wherein the malodor persists.
Another method used for removal of specific primary malodors is the physical absorption and possible temporary sequestration of the malodorous compound within the pores of a medium such as charcoal. The uses of adsorbents that will imbibe malodorous materials by ion exchange are somewhat more effective but none are non-reversible or universally binding in nature. Examples of adsorbents include the Zorbitex™ technology of OIL-DRY Corp. of America/Combe, Inc., activated carbon is used as the basis for the Odor Eaters™ technology used for foot odor control, and the triple technology used for cat litter which involves the use of odor blocking with activated carbon, use of super adsorbent polymers and the use of Arm & Hammer baking soda. The adsorption process is readily reversible and does not actively neutralize or chemically bond the odoriferous chemical species. In addition, all malodorous compounds are not able to be adsorbed. Adsorption is a selective process and limited to specific primary molecules only.
Materials like activated charcoal and some naturally occurring or synthetic aluminosilicates are often used because they physically absorb liquids or gases and dissolved lower molecular weight primary malodor molecules. Absorption is temporary due to desorption. Following physical absorption as liquid or gas, odor compounds may remain temporarily sequestered within their pores due to the nominal pore size and tightness of fit. Some molecules may potentially interact with the pore surface through weak Van der Waals forces. Adsorption materials are usually structured as large granular or pellet form so as to provide a structural mesoporous framework for harboring molecules. Pores serve as physical compartments to temporarily hold molecules. Examples include the treatment of bentonite clay with starch polymers, or polymers or agents in order to reduce dust or aid in clumping as found in U.S. Pat. Nos. 5,267,531; 5,762,023; and 5,826,543 as assigned to Nestle Purina. Another example includes the use of oil free corn germ granules as corn-based cat litter (U.S. Pat. Nos. 6,098,569; 6,216,634; 6,405,677; and 6,622,658). These adsorptive media become readily saturated and require regeneration.
Adsorption, even with weak Van der Waals force interactions, is generally a secondary characteristic of materials like activated carbon or zeolites and is dependent upon the specific structure of the molecular pore in the material. As the attraction for malodorous compounds is mostly absorption dependent, often times to help enhance the pore penetration of the adsorbing materials such as zeolite, the adsorbing materials may be pre-loaded with a surrogate molecule or ion, e.g., a cation or anion, as a means to induce ion exchange. This, however, requires a liquid environment. Consequently this approach is only partially effective for odor removal as most malodors are generally comprised of larger organic molecules and do not occur as solitary primary elemental molecules or as ionized chemical species. The approach does have some limited odor control application with small odoriferous molecules such as ammonia, hydrogen sulfide, etc.
The notable exceptions wherein adsorbents may be effectively utilized are industrial applications for hydrogen sulfide, dimethyl disulfide, dimethyl sulfide, methyl mercaptan, or sulfur dioxide removal from gaseous or liquid streams as used in pulp mills or petroleum processing. Adsorbents like activated carbon or activated alumina, however, exhibit “avalanche” effects as activated carbon beds readily fill up with entrapped species. Spent adsorbents can be recycled to remove entrapped molecules but the end products of regeneration create disposal problems of their own. A good example of this is the multi-acre recycled sulfur ponds, which are known environmental and community problems. Adsorbent materials, although they are designed specifically for the adsorption of certain low molecular weight primary malodors with application in industrial processes such as liquid or gas stream cleaning in the petroleum industry; are often misused when applied to general odor absorption. These general use applications are generally outside the scope of utility for adsorbents and the adsorbents are merely functioning as absorbents as they have a porous structure, like a sponge. Utility as such does not imply effectiveness.
The physical absorption feature exhibited by absorptive or adsorptive media can also be used as the basis for filtration, another process used for the temporary retention of odoriferous materials in liquid samples. This process is most commonly used in waste-water treatment.
The inherent problem with adsorption, absorption, and or filtration is that they are passive processes that involve no intermolecular bonding and are fully reversible based on the environmental conditions. Hence these processes do not remove malodors, per se, but hide them for a period of time, either until the media is saturated or until evaporation sets in. These are only effective as true adsorbents, with defined chemical species such as ammonia, or hydrogen sulfide and only under specific chemically engineered conditions. They are also totally ineffective against high MW malodorous compounds. Adsorbents can be effective only with odors found in the liquid or gaseous state but not in the solid state.
Another method for malodor control attempts to neutralize the malodor through interaction with another chemical, such as a salt, for example sodium bicarbonate, sodium hydrogen carbonate, phosphate salts, or esters of phosphoric acid, isomorphous double salts that are hydrated sulfates of univalent cations (e.g., potassium, sodium, ammonium, cesium, or thallium) or trivalent cations (e.g., aluminum, chromium, manganese, cobalt, or titanium) commonly referred to as alum, to neutralize the malodor. Prohibitively massive quantities of chemical salt would be required to stoichiometrically neutralize all the odor molecules, which is not practical relative to the application. This process is reversible, making it only temporary, and its effectiveness is limited to the mass of the chemisorbing species. So, in spite of neutralization, the malodors return. For example, sodium bicarbonate (U.S. Pat. No. 6,962,129; Church and Dwight) is used routinely to neutralize odors, but as noted above, reactions are reversible allowing malodors to return and require large quantities of chemical to be used with any efficacy. The neutralized chemical also needs to be removed and can become pasty in applications if it becomes wet. The neutralization approach is limited to certain types of odor compounds, provided they are chemically compatible, and thus it cannot be applied to all gaseous malodors and is generally ineffective against non-gaseous odors with the noted exception of transient interaction.
Another method infrequently used for malodor control is counteraction. This involves the use of two odors (one malodorous and one not) which when brought into proximity of each other (but not mixed) result in a temporary reduction of the overall odor. This process is termed neutralization or neutral scent when no odor results and reodorization when a milder, more pleasant odor replaces the malodor. This process involves pairs of odorants that neutralize each other's respective odors through the utilization of Zwaardemaker conjugates. This process is the basis for some consumer products. Counter-reactants are malodor specific and different formulations are required for sulfur-based odors, nitrogen-based odors, and other common cooking odors. Effectiveness of those counter-reactants can be enhanced through use of electrostatic polymers and viscosity modifiers.
A more recent approach has been the use of enzymatic compounds to attempt to enzymatically cleave the malodorous compounds to render them ineffective. These enzymes are only effective on certain protein or carbohydrate-based odors. Enzymes are used to cleave protein, carbohydrate, or lipid based material to yield non-odoriferous compounds. The action of these materials is limited as their functional groups are narrowly selective with limited cleavage specificity and each enzyme can be costly not only to develop, but to produce. The requirement exists that the sample must contain a malodor compound for which the enzyme has specificity. Examples include lysostaphin (U.S. Pat. No. 6,794,350), the enzyme-based product of America's Preferred, Inc. Specialty Chemical Products (Santa Ana, Calif.), or the use of carbohydrate oxidase U.S. Pat. No. 7,270,814), among others. Enzymes are readily inactivated by surfactants or germicides and trace quantities found in shampooed carpets renders this method ineffective.
The natural processes of enzymatic and microbial breakdown are involved in accelerated decay. These processes are part of natural decomposition but the decay process takes time and is slow. During decay a variety of malodorous compounds are released in solid, liquid, and gaseous form. Although the end result of accelerated decay is decomposition, malodorous compounds are the major by-product over time. It is the by-products of decay that are particularly malodorous and most difficult to get rid of as the by-products are composed of diverse high molecular weight organic compounds not easy to identify, treat, or eliminate due to their molecular complexity and diversity over time as the result of entropic decay and flux.
Another method for malodor control has been passive molecular entrapment. As example, cyclodextrin is a soluble ring-like structure composed of six to twelve glucose molecules. The ring-like structure of cyclodextrin is open on both sides similar in concept to a bowl without a bottom or top. It has been promoted for use to absorb any molecule that would fit into the ring. U.S. Pat. No. 6,987,099, for example, refers to the use of non-complexed cyclodextrin compositions with primary application on fabrics. The molecule has no ability to permanently bind or entrap any molecule that is absorbed into the ring structure. Any absorption is coincidental at best wherein the probability of absorption or desorption is 50/50 at best. Weak electrostatic interactions may play a part. U.S. Pat. No. 6,987,099 notes that small molecules are not sufficiently absorbed by cyclodextrin molecules because the cavity of the ring structure is too large to adequately hold smaller malodorous compounds like ammonia, and the ring structure is too small to adequately hold larger malodorous compounds found in human perspiration. Also pointed out is that cyclodextrin, as a food source, readily supports the growth of microorganisms especially in aqueous environments. Hence, cyclodextrin has to be used in conjunction with antimicrobials and surfactants in order to reduce growth of microorganisms and to promote passive entrapment of molecules capable of being temporarily held in the ring structure. The need to use cyclodextrin in a sterile environment greatly limits its use, as malodorous environments are riddled with microbes.
Numerous attempts have been made to increase the absorption and retention of molecules in the open ring structure of cyclodextrin and have included the use of cyclodextrin at high solute concentrations (in spite of its solubility limit of 1.85%), use of mixtures of cyclodextrin to achieve overall soluble concentrations up to 20%, use of anti-microbial agents, use of cyclodextrin compatible surfactants, use of salts, humectants, and/or perfumes. Presumably, if cyclodextrin were indeed effective at odor removal, it would be effective on scents and perfumes as well, which it is not. Although the material has been promoted as being effective in odor removal, in reality it is a soluble material that is ineffective in and of itself. In some instances, it may augment malodor masking through temporary entrapment, giving it minimum effectiveness at best.
Malodors are generally caused by the presence of organic compounds, such as those containing thiol or amine functionalities, or inorganic compounds such as sulfur, sulfur dioxide, or nitrogen dioxide, and are typically generated by the standard biological processes of living systems, such as excretory processes or decomposition of organic matter. Malodors may occur in liquid, solid, or gaseous form, and malodorous chemicals are diverse in terms of size, physical properties, structural features, and they change in both molecular size and diversity over time during decay
Silica-based compositions for odor control have been described, for example, in U.S. Pat. Nos. 5,970,915 and 7,037,475. These publications teach the use of underived silica gel, which functions as a desiccant, thus trapping water along with any polar odor molecules dissolved therein.
Inclusion compounds have received some use as delivery vehicles for sanitizing agents. Applications have utilized preformed inclusion compounds as partial clathrates as the means for delivering a deodorizing agent (as a guest moiety) which is subsequently released from the temporary inclusion compound to sanitize and indirectly treat odors but have not been used for malodor control wherein the malodor is the guest moiety. U.S. Pat. No. 5,382,571 describes the use of preformed clathrates of peroxyacids as the guest moiety. (Although called a clathrate, these moieties would more correctly chemically be called inclusion compounds in that the guest moiety is not fully enclosed and a full cage structure is not utilized.)
In contrast, the present invention employs mixed clathrates where the malodor is itself an entrapped guest moiety and while the present invention provides a multiplicity of examples of removing malodorous compounds, similar approaches are employed to remove other undesirable particulate or non-particulate environmental contaminants such as molds, spores, microorganisms, algae and the like.
The present invention thus provides a new approach to removing undesirable elements in the environment (that vary in molecular diversity, complexity, molecular weight, structure, size and shape from small molecules to macromolecules, in addition to constantly fluxing over time through decay) by spontaneously forming mixed host clathrates in the presence of the contaminants as guest moieties wherein these mixed clathrates form molecular and or supramolecular entrapments that form nanocages conformationally and anti-symmetric to the guest moieties.